This invention relates to a technology of processing data managed by a database using an index.
In recent years, introduction of the radio frequency identification (RFID) has rapidly increased the scale of a database for storing data such as transaction data and traceability data. Further, there has increasingly arisen a need to use such a large-scale database for business analysis and sales analysis and to apply results thereof to business. The data size is expected to exceed 100 terabytes, and be on the scale of petabytes.
Business analysis and sales analysis are conducted from various perspectives, and therefore a database processing system is required to process ad hoc queries for large-size data at high speed. JP 2007-34414 A discloses, to meet the need as described above, a database processing system capable of processing ad hoc queries for large-size data with high efficiency.
In the database processing system disclosed in JP 2007-34414 A, tasks are dynamically generated at the time of execution of a query, and the plurality of generated tasks are executed in parallel to one another. Then, in order to read data stored in a secondary storage system constituted by a plurality of disk devices such as hard disk drives (HDDs) at high speed, the plurality of tasks issue input/output requests (hereinafter, referred to as “I/O requests”) respectively.
The I/O requests issued by the tasks are executed in parallel to one another in the plurality of disk devices that constitute the secondary storage system, and hence may be processed in a short time period. Further, the multiply-issued I/O requests are scheduled so that a seek time and a rotational latency can be shortened, in consideration of the location of the head of the HDD and the location of the read request target data in the HDD as well as an issuance order of the I/O requests. Accordingly, the I/O request processing time period can further be shortened.
In addition, “Understanding the LINUX KERNEL, THIRD EDITION” authored by Daniel P. Bovet et al., published by O'Reilly Media, Inc., pp. 560-598 discloses a technology in which a database processing system or an operating system queues a plurality of I/O requests and schedules the queued I/O requests, to shorten an I/O request processing time period. Specifically, the database processing system or the operating system specifies an access destination logical block address (LBA) for each of the plurality of queued I/O requests, and changes an output order so that the seek time and the rotational latency of the HDD can be shortened.